1. Technical Field
The invention relates to a display device and, more particularly, to a display device that includes a light amount detecting device having a sensitivity correction function in consideration of degradation of a photosensor and may be manufactured in a simple process.
2. Related Art
An known existing light amount detection circuit utilizes the relationship that a leakage current from a thin film transistor is proportional to the amount of light received, makes a voltage detecting capacitor charge or discharge electric charge by the leakage current, and then monitors a voltage variation between both ends of the capacitor to thereby detect the amount of light (for example, see JP-A-2006-29832). Incidentally, it is generally known that the leakage current from the thin film transistor is proportional to the amount of light received; however, the sensitivity, which is a leakage current value against the amount of light received, decreases due to light exposure. Thus, in the photodetection circuit described in JP-A-2006-29832, because of the decrease in sensitivity, the accuracy of light amount detection decreases.
In order to prevent such a decrease in detection accuracy, a known photoelectric conversion element modifies a method of producing a thin film transistor to improve the antidegradation property (for example, see JP-A-9-232620).
However, the photoelectric conversion element described in JP-A-9-232620 requires a special manufacturing condition, so manufacturing cost problematically increases. Specifically, when a photosensor is provided inside a display device that uses a thin film transistor or when a display device and a photosensor are manufactured by the same equipment, it is impossible to manufacture the photosensor together with a driving transistor of the display device. Thus, it is necessary to add a manufacturing process or set a complex condition in a manufacturing equipment.